| 1. |
- Hammar, Arvid, 1986, et al.
(författare)
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Optical designs for a multi-beam 340 and 625/640 GHz Spaceborne climate research instrument
- 2015
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Ingår i: 26th International Symposium on Space Terahertz Technology, ISSTT 2015.
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Konferensbidrag (refereegranskat)abstract
- We report on an ongoing study where different optical configurations for a multi-beam limb-viewing (four to eight receiver channels at 340 and two channels at 625 GHz) space-borne instrument for climate research are presented and compared. The optical configurations are analyzed in terms of optical performance (gain, side lobe levels, beam efficiency etc.), weight and size of the overall instrument envelope. Using ideal fundamental Gaussian beam modes and numerical tools relying on ray-tracing and physical optics methods, the different configurations are designed and evaluated. Preliminary results indicate that a 1.3 m × 0.65 m primary reflector can be used in a configuration that includes a relay optics system having two to four elements. In addition to the limb-viewing instrument, there will be an additional instrument operating at 640 GHz for observing clouds in nadir mode.
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| 2. |
- Hammar, Linus, 1979, et al.
(författare)
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Assessing ecological risks of offshore wind power on Kattegat cod
- 2014
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 66, s. 414-424
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Tidskriftsartikel (refereegranskat)abstract
- Offshore wind power is expanding with particular development plans in the Baltic and the North Sea. To reassure an environmentally acceptable development, regulatory authorities need to make informed decisions even when evidence and experience are scarce. In this study Ecological Risk Assessment (ERA) has been applied on a wind farm project in Kattegat, proposed within a spawning ground for the Kattegat cod, a threatened population of Atlantic cod (Gadus morhua L). Six stressors with potential impacts on cod and related to wind farms were investigated. Three of them - extreme noise from pile driving, noise from vessels, and disturbances due to cable-trenching - are related to the construction phase, while lubricant spills and noise from turbines together with electric fields from cables are related to the operation phase. The ecological risk was derived from the combined likelihood and magnitude of potential adverse effects from stressors to the cod population using a weight-of-evidence (WOE) ranking procedure. Available evidence was evaluated based on its reliability, and contradictory arguments were balanced against each other using evidence maps. The option of performing hazardous construction events (e.g. pile-driving) outside biologically sensitive periods was incorporated in the assessment. It was shown that the construction of the wind farm poses a high risk to cod, as defined by the ranked and combined likelihoods and magnitudes of adverse effects. However by avoiding particular construction events during the cod recruitment period ecological risks can be significantly reduced. Specifically for this case, ecological risks are reduced from high to low by avoiding pile-driving from December through June, which confirms previous indications that pile-driving is the most ecologically hazardous activity of offshore wind power development. Additional risk reduction is achieved by avoiding cable trenching from January through May. The study thus illustrates the effectiveness of time-planning for risk reduction. Importantly, the study illustrates how combined ERA and WOE methods can be valuable for handling uncertainties of environmental impacts within offshore industrial development. (C) 2014 Elsevier Ltd. All rights reserved.
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| 3. |
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| 4. |
- Perry, Diana, et al.
(författare)
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Temperate fish community variation over seasons in relation to large-scale geographic seascape variables
- 2018
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 75:10, s. 1723-1732
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Tidskriftsartikel (refereegranskat)abstract
- In shallow-water marine environments, ecosystem functioning is a complex interworking of fine-scale characteristics and region-wide factors, and the importance of these variables can vary on multiple temporal and spatial scales. This underwater video study targeted seasonal changes in the fish community of seagrass habitats along the Swedish west coast and the influence of offshore seascape variables (latitudinal position, wave exposure, open ocean, and deep water). Results showed that fish assemblage structure exhibited seasonal changes between summer and autumn and strong spatiotemporal variations in the importance of offshore factors affecting shallow-water fish communities. In summer, abundance from the Gobiidae family responded to wave exposure, whereas the Gadidae family and juvenile migrant habitat preference guild responded to latitudinal position and proximity to deep water. In autumn, deep water was related to abundance of Gadidae and juvenile migrants, whereas latitudinal position influenced Gasterosteidae. These findings underscore the importance of understanding the influence of offshore factors on facets of coastal fish assemblages to address large-scale geographic connectivity along nearshore–offshore gradients.
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